pub fn new_count_distinct(input_str: &str) -> usize {
    //统计不重复元素个数,元素在input_str中以逗号分隔
    //支持多个字符的元素，如"Cd"

    let mut count = 0;
    let mut set = std::collections::HashSet::new();
    for s in input_str.split(',') {
        if set.insert(s) {
            count += 1;
        }
    }
    count
}
